In recent years, it is required to extremely decrease a circuit conductor width and an insulating space between circuits in printed wiring boards, for mounting electronic parts such as semiconductor parts used for electronic devices and also for achieving super-high densification of semiconductor circuits. Conventionally, electrolytic copper foils having a remarkably-roughened mat surface, which are excellent in copper foil adhesive strength, have been used as copper foils for copper-clad laminates for use in printed wiring boards. These electrolytic copper foils have excellent adhesive strength. However, when a fine circuit is formed using such an electrolytic copper foil by an etching process, parts of convex portions of the copper foil are apt to remain on the surface of a resin for insulation under the influence of the roughness of the copper foil mat surface. When an etching time is prolonged for removing the remaining convex portions completely, the circuit is etched too much so that the location accuracy or adhesive strength of the circuit is decreased.
For overcoming these problems, so-called low-profile copper foils with controlled surface roughness have become commercially practical. When these copper foils are used for copper-clad laminates of high-heat-resistant thermosetting resins, etc., which basically have a weak adhesive strength, the lack of adhesive strength is a problem about fine circuits. This greatly obstructs the formation of ultra-fine lines. In addition, for improving the adhesion strength between a copper foil and a resin for insulation, a method in which an insulating adhesive layer is formed on a copper foil has become commercially practical for a long time. For example, a technology in which a phenol•butyral resin is formed on a copper foil is known in regard to paper phenol resin copper-clad laminates, and a technology in which an epoxy resin adhesive agent is formed on a copper foil is known in regard to glass epoxy resin copper-clad laminates. As specific examples of these adhesive agent-attached copper foils, a copper-clad laminate using a copper foil on which a thin adhesive agent layer is formed (for example, JP-A-8-216340) and a copper-clad laminate using a copper foil to which a semi-cured resin film is bonded (for example, JP-A-9-011397) are proposed. Copper-clad laminates using such adhesive agent-attached copper foils have problems in terms of the degree of adhesive strength or heat resistance after moisture absorption. Therefore, further improvements are required.